This invention relates to improvements in and relating to mixers for continuously mixing fluids and, more particularly, to improvements in and relating to mixers for continuously mixing fluids which are adapted to be provided in the material supply pipe extending from a slurry tank associated with a paper making machine in the paper pulp industry and which eliminates ununiform concentration distribution of materials being conducted through the material supply pipe.
In the paper pulp industry, in order to stabilize and rationalize the operation on a paper making machine, it is strongly desired that the concentration of pulp is controlled with a high precision. As well known in the paper pulp industry, the pulp concentratin control referred to hereinabove is performed by infusing dilution water into a flow of slurry (the term "slurry" employed herein means gruel state pulp) flowing in a flow path, determining the concentration of the diluted slurry downstream of the dilution water infusion point and regulating the infusion amount of the water based on the determination result. Thus, although the mixing of slurry and dilution water may be satisfactorily attained in the zone of the flow path between the dilution water infusion and concentration determination points of the path, it is quite important that the pulp concentration control be performed with a higher precision. Therefore, in order to improve control precision of pulp concentration, it has been proposed that various mixers are provided in the slurry flow path upstream of the concentration determination point and the arrangement has provided appreciable effects.
As the prior art mixers, there have been known the agitation type mixer in which the rotary shaft is provided with the agitation wings or pawls and the static type mixer in which the screw plate is disposed within the body which is connected to a midway of a piping. The former agitation type mixer requires a substantial operation power and is also vulnerable to damage subjected to physically external force and thus, of late, the static type mixer has been widely employed.
The prior art static type mixer is schematically shown in FIG. 4 of the accompanying drawings. In the static type mixer employing the screw plate 24, flows of materials are mixed together only through energy exchange between portion of energy in the flow directions of materials flows flowing along the screw plate 24 and the screw plate 24 and thus, in order to provide a desired mixing effect, it is necessary to reduce the spiral pitch of the screw plate 24 to thereby increase the number of twists. Otherwise, since portions of material flows having different concentrations merely replace their places, a desired mixing effect cannot be obtained. As a result, the static type mixer is troublesome in fabrication and expensive. The static type mixers have a substantial length (the practical mixers now in operation comprise 5 to 8 screw plates, each having one twist, arranged in series and have the full length from 3-5 m) and thus, such static mixers are subjected to limitation with respect to their installation location. And the prior art static mixers have the drawback that pressure loss in the mixers is substantial.